Field
The present disclosure relates generally to communication systems, and more particularly, some examples relate to an apparatus and method for controlling voltage supply sensitivity of a ring oscillator.
Background
A wireless device (e.g., a cellular phone or a smartphone) may transmit and receive data for two-way communication with a wireless communication system. The wireless device may include a transmitter for data transmission and a receiver for data reception. For data transmission, the transmitter may modulate a transmit local oscillator (LO) signal with data to obtain a modulated radio frequency (RF) signal, amplify the modulated RF signal to obtain an output RF signal having the desired output power level, and transmit the output RF signal via an antenna to a base station. For data reception, the receiver may obtain a received RF signal via the antenna, downconvert the received RF signal with a receive LO signal, and process the downconverted signal to recover data sent by the base station.
The wireless device may include one or more oscillators to generate one or more oscillator signals at one or more desired frequencies. The oscillator signal(s) may be used to generate the transmit LO signal for the transmitter and the receive LO signal for the receiver. The oscillator(s) may be required to generate the oscillator signal(s) to meet the requirements of the wireless communication system with which the wireless device communicates.
A ring oscillator used in a phased locked loop (PLL) may have poor power supply rejection. Accordingly, use of the ring oscillator in the PLL may be improved by regulating a power supply.
Moreover, the ring oscillator may be used in a voltage-controlled oscillator (VCO)-based quantizer for supply sensing. The ring oscillator can translate a supply voltage into frequency and then digitized. Accordingly, it may be desirable to implement a VCO that is very highly sensitive to the supply voltage in order to achieve high digital resolution.